Use a debugger, you filthy barbarians. Learn how to step through, set breakpoints, watches, and watchpoints. Learn where to use these tools effectively. Print statements cannot give you a fine-grained view into the evolution of your program by stepping through, line by line or even instruction by instruction. Debuggers can.

Debugging by printf() is only extant because the debugging tools generally available under Unix are stone-knives-and-bearskins compared to other environments (Windows comes to mind).